(Supported in part by travel grants to D. Wheatley from the Wellcome Trust and the Carnegie Foundation). Chlamydomonas are unicellular organisms that possess two flagella (i.e., they are biflagellates). Over the years a large number of flagellar mutants of Chlamydomonas have been isolated including one with a paralyzed flagellum. Our previous results suggested that the microtubule axoneme forming the core of the primary cilium can be cut by laser microsurgery without damaging the ciliary membrane. Under this condition we observed no repair or re-growth of the primary cilium axoneme. Is the axoneme rendered "non repairable" by the laser cut? To answer this question, we are repeating the classic Rosenbaum experiments on Chylamdomonas, using the laser cutter. We are also performed laser microsurgery on PtK1 cells in order to cut primary cilia shafts. Our goal is to repeat the Rosenbaum experiment on bi-ciliated mammalian cells, and to accumulate enough interesting re sults for a joint grant proposal.